More than three decades ago my students and I at Lund University in Sweden, along with other teams, developed "fishing nets" of sorts that worked at the nanometer scale. The nets we created could trap living cells and, later, smaller biological entities, such as enzymes or other molecules. Under the right conditions, our "catches" could continue to do their usual tasks outside of living organisms for months.
The technology proved attractive for dozens of applications [see "Enzymes Bound to Artificial Matrixes," by Klaus Mosbach; Scientific American, March 1971]. For instance, plastic nets containing Escherichia coli cells are used today to produce aspartic acid, an amino acid used in the preparation of various medicines. In the food industry, plastic embedded with a specific enzyme converts the sugar glucose into fructose, which is much sweeter. A different net-and-enzyme combination has even helped to fabricate the precursors of the plastic material that makes up the nets. And, to our delight, potential applications for the traps keep arising, including in medicine. Notably, cells held in the nets might replace ones that have died or malfunctioned, such as the insulin-producing cells that are needed by diabetics.